Biosensor Analysis of β-Lactams in Milk: Comparison with Microbiological, Immunological, and Receptor-Based Screening Methods

Abstract

Abstract Two recently developed surface plasmon resonance biosensor assays for detection of β-lactams in milk were used to screen raw producer milk samples. Both assays use a β-lactam receptor protein with carboxypeptidase activity for detection. The results of the biosensor assays were compared with those of various commercial screening tests, i.e., the Delvotest SP, Penzym S, Beta-STAR, SNAP, and Parallux. The results of the 2 biosensor assays showed good agreement with those of the other screening tests. Of 195 analyzed milk samples, the results of only 5 samples differed between the assays. Additionally, 30 milk samples with both negative and positive results in the screening assays were analyzed by liquid chromatography for identification and quantification of any β-lactam residues. All screening tests showed 0% false-negative results with 15 incurred samples containing between 4.0 and 268 μg/kg penicillin G. The biosensor assays showed 27% positive results (false violatives) with 15 producer milk samples containing penicillin G concentrations between 0 and 3.6 μg/kg, i.e., below maximum residue limit. This figure varied between 27 and 53% for the other screening tests.